Abstract: The Yangcheng tunnel mainly passes through the loess stratum, soil-sand interface strata, completely weathered red sandstone stratum, etc. in the paleogully. During the construction, large deformation and cracking of the initial support were encountered. Based on the physical and mechanical tests, field monitoring and measuring as well as the numerical simulation, it studies the deformation and stress behaviors of the initial support structure of the tunnel crossing various strata in the paleogully. The study conclusions are as follows: 1) although the cohesion of sandy loess is larger, the compressive modulus and internal friction angle of the completely weathered red sandstone are larger; 2) the tunnel displacements in the soil-sand interface strata are complex and variable, with the values being still between the displacements in the loess stratum and the completely weathered red sandstone stratum. The tensile stresses would appear at the arch foot in the completely weathered red sandstone stratum and at the interface of the soil-sand strata, which should be paid attention to during construction; 3) the deformation law in the numerical simulation is the same as that in the field test. Unlike conditions in the loess and red sandstone strata, as for the soilsand interface strata, the minimum principal stress at the upper part of the interface is larger than that at other locations, and the maximum principal stress at the interface is slightly larger than that at the arch foot.